The 28-year-old is set to undergo tests on Wednesday evening to determine the severity of the injury he suffered in training but Black Cats coach Dick Advocaat expects him to be out for a lengthy spell.
"Adam will go to the hospital for a scan tonight and then we will know exactly what is wrong," Advocaat told the club's official website.
"It is a serious injury and it will be at least eight weeks."
Johnson started Sunderland's 4-2 defeat by Leicester on the opening day of the Barclays Premier League season last weekend and played a full 90 minutes.
The England international is due to face trial for child sex charges at Bradford Crown Court on February 10 next year.
He has already denied three counts of sexual activity with a child and one count of grooming.
Advocaat also confirmed that midfielder Jordi Gomez remains unavailable and striker Danny Graham is struggling for fitness.
The 67-year-old added: "We have Jordi Gomez and Adam Johnson injured and Danny Graham also has some minor problems."
Source : PA
Source: PA